1. Technical Field
The invention is an improvement in cordless remote telephone systems.
2. Background Art
An ordinary telephone requires relatively little power to operate, and therefore derives sufficient power directly from the telephone line to operate, and need not be plugged into a household power receptacle. Therefore, it is a reliable communication unit, especially during local power outages and is portable to any location having a telephone jack.
Cordless remote telephone systems typically include a base unit connected directly to the user's telephone line and a remote unit with a hand-set, the remote unit and the base unit communicating with each other via a radio link. Typically, the base unit requires 110 volts AC and so must be near a household electrical power receptacle, while the remote unit is powered by rechargeable batteries. The advantage of such a system is that the user may take the remote unit anywhere within the range of the radio link between the two units without having to connect the remote unit to a power source or to the telephone line. The remote unit functions in the same manner as a normal telephone, as far as the user is concerned.
The problem with such a system is that, while the remote unit is independent of other power sources, it cannot function whenever the base unit looses power, because the base unit links the remote unit with the telephone line. Thus, the system cannot be used where household power outlets are unavailable or during a power failure, notwithstanding the independence of the remote unit from other power sources. This places the cordless remote telephone system at a distinct disadvantage relative to ordinary telephones.
This problem appears to be difficult to overcome, particularly because of the power required by each unit during transmission to the other unit. In view of the relatively large amount of power required by the transmitter circuits, the remote unit typically employs rechargeable batteries, a battery charger being provided conveniently in the base unit or other apparatus. Thus, the requirement for a household current source is now two-fold: to provide transmission (as well as receiving) power for the base unit and to provide battery-recharging power through the base unit (or other apparatus) for the remote unit's batteries. Thus, it would not seem possible to provide a practical system in which both the base and remote telephone units are independent of a household power source.
It is therefore an object of the invention to provide a cordless remote telephone system, including a base unit and a remote unit, which is truly independent of other power sources and which is therefore operable at all times and at any location having a telephone line, regardless of the availability of electrical power outlets.